GaAs MESFET ring oscillators were fabricated on a Si substrate and successfully operated. Epitaxial techniques to grow a GaAs layer on a Si substrate were investigated. The device-quality GaAs epitaxial layer was obtained by introducing a Ge layer (by ionized cluster-beam deposition) and alternating GaAs/GaAIAs layers (by MOCVD). The typical transconductance of 140 mS/mm was obtained for the FET with a 0.5 µm × 10 µm gate. The minimum delay time was 66.5 ps/ gate at a power consumption of 2.3 mW/gate.